1. The problem statement, all variables and given/known data A boy standing in an elevator accelerating upward throws a ball upward with a vo. The ball returns to his hands after time t. The acceleration of the lift is 2. Relevant equations 3. The attempt at a solution After time t, displacement of the ball = displacement of the lift vo t - 1/2 gt2 = ? What should the displacement of the lift be? According to me, it should be ut + 1/2at2. Problem is, I don't know what the initial velocity of the lift is, i.e. what u is. What do I do?